1. Field of the Invention
The present invention relates to a vehicle suspension for an automobile or the like, and more particularly to a front suspension for a vehicle.
2. Description of the Prior Art
In a vehicle such as an automobile there is a well known phenomenon termed "flutter" in which the suspension and steering systems resonate because of non-uniformity and unbalance in the vehicle wheels. The flutter is perceived by the driver as a rotational oscillation of the steering wheel. Also is well known another phenomenon termed "harshness" in which the wheel tire is given a bump by a seam in the pavement of the road or the like and the suspension and steering systems are percussively driven to turn rearward, with a simultaneous generation of unpleasant crashing sound and also a shock perceptible at the steering wheel and the seat.
The construction described in U.S. Pat. No. 4,448,441 is known as one means of reducing flutter in a strut type front suspension including an L type arm or A type arm, in other words a suspension having a vehicle wheel support member which supports rotatably a vehicle wheel, a control arm which at its inboard end is pivotally attached to the vehicle body at two coupling portions spaced apart substantially in the vehicle longitudinal direction with elastic linkage bearings interposed at front and rear and at its outboard end is pivotally attached to the vehicle wheel support member, a strut which at its lower end is coupled to the vehicle wheel support member and at its upper end is pivotally attached to the vehicle body and a knuckle arm which is provided integrally with the vehicle wheel support member and is pivotally attached to a tie rod at a position to the rear of the pivot point of the vehicle wheel support member and the control arm. In this U.S. Pat. No. as shown in FIG. 1 and FIG. 3 therein, the axis (54) joining the upper support (42) and the center (58) of oscillating movement in the longitudinal direction of the control arm either passes close to the axis (49) of the tie rod or intersects the axis of the tie rod, whereby vibration of the tie rod along its axis due to vibration in the vehicle longitudinal direction of the control arm is reduced or prevented, as a means of reducing or preventing flutter.
In the case of the above mentioned U.S. Pat. No. in order that the axis (54) joining the center of motion in the vehicle longitudinal direction of the control arm with the upper support is close to the axis (49) of the tie rod or intersects with that axis, it is necessary that: [1] the spring constant of the front elastic linkage bearing is made substantially equal to the spring constant of the rear elastic linkage bearing. Furthermore, [2] in order to improve the steering stability it is necessary to make the front elastic linkage bearing harder in order to increase the lateral rigidity of the suspension; and [3] in order to reduce harshness it is necessary to make the rear elastic linkage bearing softer. It is not possible for [1], [2] and [3] to hold at the same time, so with the construction described in the above mentioned U.S. Pat. No. it is not possible simultaneously to reduce flutter, reduce harshness and improve steering ability.
Furthermore, in the construction described in the above mentioned U.S. Pat. No. the assumption is made that even in the event of flutter the vehicle wheel support member and knuckle arm do not move horizontally about the kingpin axis and also that the pivot point between the knuckle arm and the tie rod moves only about the axis 54; thus with the construction described in the above mentioned U.S. Pat. No. there is the problem that effective reduction or elimination of flutter cannot necessarily be obtained.